Diaphragm activation via bilateral electrical stimulation of the phrenic nerves is a useful therapeutic modality providing artificial ventilatory support in ventilator dependent tetraplegic patients. Unfortunately, most patients with ventilator dependent quadriplegia are not candidates for phrenic nerve pacing due to partial or complete phrenic nerve injury. Based upon recently completed clinical trials, a coordinated contraction of the inspiratory intercostal muscles can be produced via a single electrode placed on the epidural surface of the spinal cord. Due to the production of smaller inspired volumes compared to diaphragm stimulation, intercostal muscle pacing alone provides only short term ventilatory support. However, full time or near full-time ventilatory support can be achieved with combined intercostal and unilateral diaphragm pacing in ventilator dependent tetraplegic patients. In each of 4 patients studied, full-time or near full-time ventilatory support was achieved. Each patient has reported less physical restriction, improved sense of smell, greater confidence in social situations and improved speech. While successful, the equipment utilized in this trial has significant limitations precluding further clinical studies and the potential for commercialization. Moreover, we have demonstrated in recent studies that the diaphragm can be activated less invasively via intramuscular diaphragm electrodes. The specific aims of Phase I of this project encompass the design, fabrication and bench testing of a new intercostal pacing system which can interface with the Case Western Reserve University (CWRU) implantable receiver-stimulator which: a) provides the necessary stimulus parameters for intercostal muscle activation and b) can be used to synchronously activate the diaphragm via intramuscular electrodes, allowing combined intercostal and diaphragm pacing. In Phase II, this device will be tested initially in animal studies and subsequently in human clinical trials. If successful, this device would eliminate the disadvantages of the currently existing systems and allow patients with only unilateral diaphragm function to achieve the same benefits as patients undergoing bilateral phrenic nerve stimulation. [unreadable] [unreadable]